1H-Pyrrolo-[1,2-b][1,2,4]triazole derivatives are useful as synthesis intermediates of physiologically active substances such as pharmaceutical preparations and pesticides. These derivatives are also known as coupler nuclei and dyes which exhibit reduced secondary absorption in the field of photographic chemistry (proceedings of the 60th Annual Conference of The Society of Photographic Science and Technology of Japan). However, 1H-pyrrolo-[1,2-b][1,2,4]triazole dyes which have heretofore been known exhibit a maximum absorption wavelength of lower than 560 nm. No 1H-pyrrolo-[1,2-b][1,2,4]triazole dyes which exhibit a maximum absorption wavelength of higher than 600 nm have been known.
In recent years, 1H-pyrrolo-[1,2-b][1,2,4]triazole dyes which exhibit a maximum absorption wavelength of higher than 560 nm, particularly 600 nm have been desired. In other words, dyes containing a 1H-pyrrolo-[1,2-b][1,2,4]triazole nucleus which exhibit reduced secondary absorption and a primary absorption wavelength of higher than 600 nm have been keenly desired.
Furthermore, in recent years, new color image formation methods such as color electrophotography, ink jet printing process and heat-sensitive transfer process have been proposed. On the other hand, with the development of electronic imaging technique, the demand for solid state image pick-up tube and filter for color liquid crystal television set has increased. Thus, azomethine dyes have been applied and reviewed in color photography as well as various systems or merchandise.
As cyan azomethine dyes in these applications there have been known phenol and naphthol azomethine dyes. Furthermore, imidazole azomethine dyes and hydroxypyridine azomethine dyes have been known.
Moreover, pyrazoloazole azomethine dyes, pyrazolopyrimidin-5-one azomethine dyes, pyrazoloquinazolone azomethine dyes, pyrazolotriazine azomethine dyes and cyan azomethine dyes have been known.
However, these known azomethine dyes have various disadvantages. For example, phenol and naphthol azomethine dyes exhibit too broad an absorption to serve as dyes for filter. Further, imidazole azomethine dyes are disadvantageous in that they exhibit a low fastness to light. Moreover, pyrazolopyrimidin-5-one azomethine dyes, pyrazoloquinazolone azomethine dyes and pyrazolotriazine azomethine dyes exhibit too broad an absorption. Further, pyrazolotriazole azomethine dyes exhibit a low fastness to light. Moreover, hydroxypyridine azomethine dyes can hardly be synthesized and exhibit a low fastness to light.
Thus, among known azomethine dyes, there are no dyes which exhibit an absorption waveform suitable for cyan color and a high fastness to light and heat. Therefore, the development of azomethine dyes which exhibit a sharp absorption and a high fastness has been keenly desired.
In order to overcome these difficulties, the inventors made a study on novel azomethine dyes. As a result, it was found that pyrrolotriazole azomethine dyes having a specific structure which has never been known exhibit a sharp absorption and a high fastness to light. Thus, the present invention was worked out.
Pyrrolotriazole couplers are disclosed in JP-A-62-279340 and 62-278552 (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
Even if the foregoing techniques are known, the present invention is by no means limited thereby.
The above mentioned known couplers are considered to undergo color development to produce azomethine dyes. According to the above cited references, the color of the dyes thus produced are magenta.
The inventors' study showed that pyrrolotriazole azomethine dyes represented by formulae (I) to (IV) given later exhibit a cyan color when its coupler portion is such that Hammett's substituent constant .sigma..sub.p of R.sup.7 is 0.15 or more and the sum of Hammett's substituent constant .sigma..sub.p of R.sup.7 and R.sup.8 is 0.65 or more.
In the above cited references, there is no reference to couplers which will give an azomethine dye that exhibits a cyan color. There is neither reference that gives an expectation of a specific structure that exhibits a cyan color.
In other words, it was disclosed for the first time by the inventors, who made a study on the relationship between the substituents R.sup.7 and R.sup.8 and the absorption characteristics of dye, that novel pyrrolotriazole azomethine dyes of the present invention exhibit an excellent cyan color. It is extremely difficult to expect this fact from the above cited references.
Moreover, in recent years, with the rapid progress of the communication industry, various data processing systems have been developed, and recording processes and apparatus suitable for these data processing systems have been developed and applied. Among these recording processes, the heat transfer recording process can be operated by means of a light weight and compact apparatus which gives no noise and excellent handleability and maintenance. The heat transfer recording process can also be operated in a color system. Thus, the heat transfer recording process has been widely employed in recent years.
Examples of the heat transfer recording process include a process which comprises heating a heat transfer dye providing material comprising a hot-melt ink layer carried on a support by a thermal head to melt the ink which is then transferred to an image-receiving material (melt transfer process), and a process which comprises heating a heat transfer dye providing material comprising a dye providing layer containing a heat migrating dye and a binder by a heat head to allow the heat migration of the dye alone to an image-receiving layer in an image-receiving material to effect recording (heat migration process, generally referred also to as "sublimation type heat-sensitive transfer process").
The present invention relates to a heat transfer dye providing material for use in the heat migration process. The term "heat migrating dye" as used herein means a dye which can undergo sublimation or diffusion in a medium to effect transfer from a heat transfer dye providing material to a heat transfer image-receiving material.
However, heat migrating dyes for use in this process have heretofore encountered various limitations. There is little heat migrating dye which fully satisfies necessary properties. Examples of such necessary properties include spectral characteristics suitable for color reproduction, ease of heat migration, insusceptibility to discoloration due to heat and light, reduced denaturation by various chemicals, insusceptibility to sharpness drop after image formation, insusceptibility to re-transfer of image, and ease of preparation of heat transfer dye providing material.
Particularly important among these properties is insusceptibility to discoloration due to heat and light. However, heat migrating dyes which have heretofore been used leave much to be desired in this respect and thus can be subject to discoloration in a slight period of time. Therefore, these heat migrating dyes have been improved from the standpoint of image preservability. Further, most of these known dyes exhibit a broad absorption. Thus, the development of dyes which exhibit a sharp absorption has been desired.